Do-it-yourself homemade UPS?

Question

Rechargeable batteries

Greetings!
There are quite a lot of 18650 elements still quite alive (from old laptops)
There is an idea to make ups for a working computer.
Question 1:
As I understand it, the charge-discharge should be controlled by the controller (if the voltage is below a certain level, we turn on charging
; if it is higher, we turn it off). Can you tell me how to control the voltage? Is it possible on arduino? Maybe there are ready-made microcontrollers for this?
Question 2:
I understand that you can buy regular UPS in the store. But 5 min. work is about nothing at all. Remote battery options are expensive and have features that are not needed at all.
Does anyone have DIY options for creating something similar?

Answer 1

Hocok_B_KapMaHe , power is measured in Watts, for example, I have one 18650 battery that can give out 40 A, with its 4 V voltage, this is 160 W of power. 4 of these batteries - and here is your 600 watts. But the total capacity of these batteries is only (2000 mAh * 4 V * 4 pcs) = 32 W * h, which is enough for the computer for 5 minutes, and even then, provided that the conversion is 4 -> 220 (and sequentially banks in different states and different capacities cannot be connected, only parallel) will be performed perfectly and the inverter will pull this.
It is best to drag used lead batteries from the store and add an inverter. This is where something can happen.